Draft and smoke control system for a furnace



Dec. 31, 1957 E. A. FIELD 2,818,060

DRAFT AND SMOKE CONTROL SYSTEM FOR A FURNACE Filed Jan. 18, 1956 IN V EN TOR.

United States Patent DRAFT'AND SMOKE CONTROL SYSTEM FOR A FURNACE Edward 'A. Field, 'Mendota, 11].; Amy Field and City National-Bank and Trust Company of Chicago, executors of the will ofv said Edward Arthur Field, deceased Application January 18,1956, Serial No. 559,839

. 9 Claims. or 126-307) This invention relates to irnprovements in draft1.and

smoke controlsystem-forafurnace. The principaLobjects of this invention are:

First, to provide a: novel means for introducing combustion air .into and axhausting combustion gasesfrom a discharge system. for .a furnace which-will eliminate back drafts through the-smoke. pipe into the-furnace.

Third, to. providea furnacewith air inletand smoke outlet-passages entirely sealed around the. furnace whereby products of combustion con; gaseous fuel cannot escape into the buildingin which the furnace :is installed.

Fourth to providea heating. system-which eliminates loss.of .heaLdue to--warmtair.-from thebuilding being drawn out through the chimney.

' Fifth, toprovide a: furnace installation which is adevquately supplied with combustion air regardless ofwthe construction. of. the building in which the: furnace .is installed and regardless of theoperation-ofappliances such as ventilating fansin the building.

Other objects and advantages of the invention will-be apparent from a consideration-of the following description andclaims. The drawings, of which there is. one-sheet, illustra'teithree highly. practical, forms vof they air supply and smoke discharge systemas: applied-to .a furnace. installed in a building.

Fi'g. 1 .isa fragmentary felevat'ional view. of .a furnace and associated chimney installed in-a. building,..\the :building being indicated conventionally. and fragmentarilyi-and portions of 'the" furnace and .chimneybeing. broken away in vertical cross section.

Fig. 2 is afragmentary horizontalcross sectional view taken along the, plane of the brokenlline.2-.-2 inEig.. 1.

Fig; 3 is afragmentary verticalucross sectionalwiew through a first modified form offthe chimney cap.

Fig. 4 is a top plan view-partially brokenaway in horizontal cross section of a second modified form of chimney "cap.

'Fig. Sis atop plan view, partiallybroken away insection of the capshown in Fig.3.

'InFig' 1 .a building, such as adw'elli-ng, is indicated conventionally by portions. of its roof at .1. IA- chimney 2 extends downwardlythroughfthe, roofdo a furnace indi- "cated generally at 3. For reasons whichwill appear. ast'he "descrip'tion'ofthe furnace and chimney progresses the. 10- cati'on' ofth'e furnacewithinthe. building is'immaterial. A chimney cap, indicated generally at 4 coactswith the chimmy and the"v furnace ..as will be. described inngreater detail. The furnace consists ofan entirelyclosedor sealedcasing; 5 having. apartitionuwall 6 diyidingthe furnace into .a plenum chamber 'landaminlet enclosure 8. Positioned withinathegtplenum chamber. is.-.a. combustion-'chambem 9 conneeted toeand.communicatingwith a heat'rerichange chamber. 10. Air tot-bmheatedapasses .Xhl'OllghflhW-PIBBUIH -.;chamber 7 between ducts 11- under the influence :of' either forced or-gravity-air flow. The details of .construc'tiontof sthecombustion chamber, plenum chamber; heat:exchange chamber-.and warm air circulating systemformsno part'of .the present invention and so arenotdisclosedin greater detail.

Positioned in the lower portion of theinletxenclosure b .is. a burner 12 that projects into the .bottom zoftrthecombustion chamber 9. The furnace is moreadvantageously adaptedfor use of a gas burnersuch. as is illustrated/but can be used toadvantage with oil or evensolid fuel burning furnaces. It will be understood that the burner 12 incorporates structure common to alliburners forrintro- .ducing primary combustion air into .the combustion cham- .ber. Secondary airas required isaalso'admitted'in the usual way either through the burner or appropriate draft openings not illustrated. A door 13 in the casing permits eaccess toitheburner forservice but is closed and substantially-sealed during operation. of theburner and the furnace.

The chimney 2 is of double'walled-construction'contsisting of an outer tubular sleeve 14 positioned in radially spaced. relation around an inner smoke'flue 15. 'Where desired a further corrosion'resistant linersuch as-avitre- ,ous enameled tube; 16 may be provided within :the smoke "pipe15. Chimneys of doubleand triple wall construc- .tion-are commonly available .as'prefabricated articles but are .usedto cool the inner flue andp'ermit installation near combustible material.

The lower end {if the" tubular sleeve 14'rests-'-on"the .topof the casing 5 and opens into the inlet enclosure-'8 .through a flanged opening'17 in the casing. 'Thesm'oke .flue. 15 projects into the'inlet enclosure 8 and-*rests' oma .smoke hood. 18- mounted on the partition wall 6. The physical location of the chimney directly vertically-over .the furnace 3 is not essential and it will-*be appre'ciated .that'the chimney'Z may have angled or horizontal reaches connecting the vertical portionwith-a laterally displaced furnace. ,1 The connections between the chimney and-*the furnace may alsobe made .in the sides of the casing' '5 and .smoke hood 18. The smoke :flue opens into' thetop of the -hoodand therbottom of the hood is open to "the inlet-en- .closure aszat 19. Asmoke pipe20 communicates through an opening' 20A between the-top 0f the heat exchange chamber 10 through the partition'fi and the smoke-hood 18' above .the. open lower side 19 of the hood so that smoke and productsofcombustion issuing from the combustion chamber through the smoke pipe 20 are directedinto the .smoke hood but escapeupwardly through the smokeflue due to the natural draft of heatedgas before spilling'downwardly through the bottom of the smoke' hood. In-some installations, particularly high capacity oil-and coalfired furnaces, the hood need not open .to the inlet chamber.

The chimney cap 4.at the top of the chimneyZ consists of a-lowercircular baflle 21 secured around the topof'the :tubular sleeve 14. A second circular baflie''22' is secured :aroundthe upper end of the smoke flue 15 in vertically spaced relation above the baffle 21 due to theextension or. projection of the smoke flue above the upper endo'f then-sleeve. A third circularbaflle 23-is positioned in spaced relation above the bafiie' 22. il ilhthree-baflles lL .22'and .23 are of approximately the samedimension' arid are interconnected by'the cylindrical: screen' 24 thatfunc- :tions towsupportv the top baffle 23 and prevent birds'from :nesting between the baflles and in the top of the chimney.

In the operation of the furnace and the 'chimneyb'oth primary and secondary combustion air is drawn in radially between-the lower two baffles 21 and22 and' descends through the annular space between the sleeve 14 and smoke .flue15 into the inlet enclosures. Primary combustion air =istthenird-rawn from the inlet enclosureinto the combustion chamber by operation of the burner in the usual manner of operation of the burner and secondary air is admitted to the fire in the usual manner from the same enclosure. Some air from the inlet enclosure may be recirculated upwardly through the open underside of the smoke hood 18 into the smoke flue 15 under the influence of the rising products of combustion and the natural draft in the smoke pipe. The products of combustion rise through the smoke flue and are discharged between the upper two baffies 22 and 23 as will be understood. Since both the inlet for combustion air and the outlet of the products of combustion are positioned in the same atmospheric area around the chimney cap 4 there can be no externally created pressure differential between the inlet and the outlet ends of the furnace and chimney system due to such variable factors as wind direction and velocity and the furnace will operate at all times directly and solely under the influence of the natural draft created by the hot gases rising through the smoke flue 15. There can be no down drafts created in the smoke flue 15 because any external pressure source such as the wind will act equally on the inlet to the sleeve 14 and on the outlet from the smoke pipe 15. This is of particular advantage when the burner 12 is a gas burner and is provided with a small pilot light which might be snuffed out by the back draft.

The system prevents the escape of partially burned products of combustion or unburned fuel gas into the building 1 because the casing is sealed and because there can be no back drafts through the smoke flue as was explained above. No warmed air is drawn from the interior of the building and permitted to escape through the smoke flue 15 so that the heating system as a whole operates with improved efficiency. No amount of variation in the interior construction of the building or change in interior pressure such as might be created by operation of a ventilating fan can change the static pressure at the inner end of the smoke flue 15 so the flow of combustion gases through the smoke flue 15 can not be accidentally reversed to fill the building with smoke.

Fig. 3 illustrates a first modified form of chimney cap in which the top baflie 23B is supported from the bottom bafiie 21B by six angularly spaced deflector plates 25. The lower baffle plate 21 is secured to the top of the chimney sleeve 14 in the same manner as in Fig. l and the middle baflle 22B is slotted to pass the plates 25 and the plates are notched as at 26 to receive and support the intermediate plate. As in the first form of the chimney cap a cylindrical screen 24 surrounds the bafiies to exclude birds. The function of the upright plates 25 is to break up or diffuse the air flow of wind directed between the horizontal bafiies. Particularly in the case of a downwardly inclined wind current such as might deflect from an adjacent high building, the undiffused air stream may build up a slight pressure in the chimney. While this pressure would be about equal in both the flue 16 and sleeve 14 it might be objectionable as causing leaks from the casing 5 and combustion chamber 10. There may even be a slight pressure differential created between the upper ends of the inner smoke flue and the outer inlet passage because wind currents passing between the upper two horizontal baflies relatively unobstructed while the same volume of air flowing between the lower two bafiies meets the obstruction of the inner smoke flue and tends to build up a slight dynamic pressure that is transmitted down the inlet passage. When the velocity is cut down this does not occur. A similar diffusing action can be obtained by substituting an expanded metal mesh for the screen 24. Expanded mesh blocks 40 to 50% of the area of the mesh and breaks up air streams so as not to create air currents into the flues.

Fig. 4 illustrates a second modified form of chimney cap in which the bottom baflie 21C is rectangular in shape and mounted on the top end of the sleeve 14. Opposite side edges of the baflie plate 210 are turned upwardly in side plates 27 that connect with and sup- 4 port the middle bafile 22C and the cover plate 23C. The smoke flue 15 projects upwardly and is connected to the middle bafiie 220 while the cover 23C is spaced above the middle bafiie as in the other forms of the chimney cap. The open ends of the chimney cap between the side walls 27 are closed by screens 24C and the chimney cap operates as the other forms of the cap to insure equal pressure conditions at the upper end of the smoke flue and at the upper end of the inlet sleeve 14.

Having thus described the invention, what is claimed as new and is desired to be secured by Letters Patent is:

1. A furnace and smoke pipe installation for a fiuid fuel burner in a building comprising a combustion chamber, a smoke pipe connected to said combustion chamher, a chimney communicating with said smoke pipe and extending exteriorly of said building, a sleeve spaced around said chimney and forming an inlet duct from the exterior to the interior of said building, a first substantially imperforate flat bafiie around the upper end of said sleeve and substantially sealed thereto, a second fiat bafile around the upper end of said chimney and spaced above said first bafiie, and a third fiat baffie spaced above and over said second bathe, and a screen connecting said battles to prevent the entry of birds therebetween, said bafiles being of equal size and forming adjacent areas of entry to said inlet and said chimney subject to equal external pressure conditions.

2. A furnace and smoke pipe installation for a fluid fuel burner in a building comprising a combustion chamber, a smoke pipe connected to said combustion chamber, a chimney communicating with said smoke pipe and extending exteriorly of said building, a sleeve spaced around said chimney and forming an inlet duct from the exterior to the interior of said building, a first substan tially imperforate flat bafiie around the upper end of said sleeve and substantially sealed thereto, a second fiat battle around the upper end of said chimney and spaced above said first bafiie, and a third fiat baffle spaced above and over said second baflie, said baflies being of equal size and forming adjacent areas of entry to said inlet and said chimney subject to equal external pressure conditions.

3. A furnace and smoke pipe installation for a fluid fuel burner in a building comprising a combustion chamber, a smoke pipe connected to said combustion chamber, a chimney communicating with said smoke pipe and extending exteriorly of said building, a sleeve spaced around said chimney and forming an inlet duct from the exterior to the interior of said building, a first substantially imperforate fiat baflie around the upper end of said sleeve and substantially sealed thereto, a second flat bafile around the upper end of said chimney and spaced above said first bafiie, and a third fiat baffle spaced above and over said second batfie, said baflies forming adjacent areas of entry to said inlet and said chimney subject to equal external pressure conditions.

4. A furnace and smoke pipe installation for a burner comprising a combustion chamber, means forming a smoke outlet from said combustion chamber, a chimney communicating with said smoke outlet and extending to an elevated position above said chamber, a sleeve spaced around said chimney and forming an inlet duct to deliver combustion air to said chamber, a first substantially imperforate fiat baffle around the upper end of said sleeve and substantially sealed thereto, a second flat baffle around the upper end of said chimney and spaced above said first bafiie, and a third flat baflie spaced above and over said second bafiie, said baffles forming adjacent areas of entry to said inlet and said chimney subject to equal external pressure conditions.

5. In combination with a furnace having an air inlet and a smoke outlet, a double walled chimney extending to an external position in the atmosphere, the walls of said chimney forming an air inlet passage communicating with said inlet and a smoke flue connected to the outlet of the furnace, spaced flat horizontal imperforate baflles on the tops of the inner and outer walls of said chimney and above the inner of said walls defining flat horizontal passages to the upper ends of said inlet passage and said flue from the same pressure area around the upper end of said chimney, and upright baffles spaced angularly around said chimney between said horizontal baffles and spaced inwardly from the periphery of said horizontal baflles to break up air streams directed between said horizontal baffles, the lower two baffles being substantially sealed to the ends of the inner and outer walls with which they are associated.

6. In combination with a furnace having an air inlet and a smoke outlet, a double walled chimney extending to an external position in the atmosphere, the walls of said chimney forming an air inlet passage communicating with said inlet and a smoke flue connected to the outlet of the furnace, spaced flat horizontal imperforate baffies on the tops of the inner and outer walls of said chimney and above the inner of said walls defining fiat horizontal passages to the upper ends of said inlet passage and said flue from the same pressure area around the upper end of said chimney, and upright baffles spaced angularly around said chimney between said horizontal baflles to break up air streams directed between said horizontal bafiles, the lower two baflles being substantially sealed to the ends of the inner and outer walls with which they are associated.

7. In combination with a furnace having a primary air inlet and a smoke outlet, a double walled chimney extending to an external position in the atmosphere, the outer wall of said chimney forming the outside of an air inlet passage communicating with said inlet, the inner wall of said chimney being spaced from the outer wall and forming a smoke flue communicating with the outlet of the furnace, and spaced flat imperforate baflies on the tops of the inner and outer walls of said chimney and above said flue defining fiat horizontal passages to the upper ends of said inlet passage and said flue completely therearound and from the same pressure area around the upper end of said chimney, the lower two bafiles being substantially sealed to the ends of the inner and outer walls with which they are associated.

8. A furnace and smoke flue installation for a burner in a building comprising a combustion chamber, a smoke pipe connected to said combustion chamber, a chimney communicating with said smoke pipe and extending exteriorly of said building, a sleeve spaced around said chimney and forming the outside of an inlet duct from the exterior to the interior of said building, a first substantially imperforate flat baflie around the upper end of said sleeve and substantially sealed thereto, a second flat baffle around the upper end of said chimney and spaced above said first baflie, a third flat baifle spaced above and over said second bafile, said bafiies being horizontal and parallel and forming adjacent areas of entry to said inlet and said chimney subject to equal external pressure conditions, and spaced upright bafiles secured between said first three baffles around the upper end of said chimney.

9. A furnace and smoke flue installation for a burner in a building comprising a combustion chamber, a plenum chamber enclosing said combustion chamber, a smoke pipe connected to said combustion chamber and extending exteriorly of said plenum chamber, a burner being arranged to maintain a fire in said combustion chamber, a chimney communicating with said smoke pipe and extending exteriorly of said building, a sleeve spaced around said chimney and forming the outside of an inlet duct from the exterior to the interior of said building, an enclosure surrounding and connecting the inner end of said inlet with the outer end of said burner, a first substantially imperforate flat bafile around the upper end of said sleeve and substantially sealed thereto, a second bafile around the upper end of said chimney and spaced above said first bafile, a third bafile spaced above and over said second baffle, said baflles forming adjacent areas of entry to said inlet and said chimney subject to equal external pressure conditions, and spaced upright bafile means secured between said first three bafiles partially obstructing air flow between the bafiles equally around the upper end of said chimney.

References Cited in the file of this patent UNITED STATES PATENTS 880,442 Colquhoun Feb. 25, 1908 989,358 Hemphill Apr. 11, 1911 1,643,705 Dykes Sept. 27, 1927 2,160,883 Lundstrum June 6, 1939 2,192,920 Linch Mar. 12, 1940 2,711,683 Ryder June 28, 1955 2,754,816 Ryder July 17, 1956 2,764,972 Ryder Oct. 2, 1956 

